Pressure sensors are used to measure pressure of target fluid. Some pressure sensors include: a joint provided with a port through which target fluid is introduced; and a sensor module provided on the joint and including a diaphragm displaceable in response to the pressure of the introduced fluid. The displacement of the diaphragm is converted into a signal and outputted.
According to a typical arrangement of such pressure sensors (Patent Literature 1: JP-A-2010-190655), for instance, a sensor module is provided on a joint, the sensor module being accommodated in a housing provided with a terminal electrically connected to a diaphragm of the sensor module through a flexible circuit board. The joint is also provided with a cap-shaped metal base, the top of the base is provided with an opening in which the diaphragm is exposed, a part of the flexible circuit board is arranged on a lateral portion of the base intersecting the top of the base provided with the opening, and an electronic component is mounted on this part of the flexible circuit board.
In this typical arrangement, outwardly projecting flanges are provided to the open end of the base at opposite positions and these two flanges are brought into contact with the vicinity of an attachment groove provided to the joint to position the base.
In the typical arrangement of Patent Literature 1, after mounted with the electronic component, the flexible circuit board is wound on the base.
It takes time and effort to mount the electronic component on the flexible circuit board and wind the flexible circuit board mounted with the electronic component on the base along the top and the lateral portion of the base.
In the typical arrangement of Patent Literature 1, the flanges, which are provided to the open end of the base at the two positions, are brought into contact with the vicinity of the attachment groove of the joint to position the base. As a result, the structure of the base becomes complicated due to the presence of the flanges. Further, the positioning of the base is necessarily performed at a position remote from the center of the base. The base is formed in the shape of an elongated cap with a length in a first direction being longer than a length in a second direction perpendicular to the first direction in a plan view, so that a cap, which is relatively wide particularly in the first direction, is present between an inner circumferential surface of the base and an outer circumferential surface of a projecting portion of the joint, which makes the positioning of the base relative to the joint difficult.
Therefore, it is not easy to accurately position the base relative to the sensor module provided to the joint. When the base is inaccurately positioned relative to the sensor module (e.g., the center of the base is misaligned with the center of the sensor module or a flat diaphragm surface of the sensor module is not parallel with a flat top surface of the base), the diaphragm and the flexible circuit board cannot be accurately bonded.